Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$176.84	7.732%	$190.5133	$190.51	$190.50	$190.50
Purchase #2	$157.46	11.600%	$175.7254	$175.73	$175.75	$175.70
Purchase #3	$68.42	3.287%	$70.669	$70.67	$70.65	$70.70
Purchase #4	$74.90	10.469%	$82.7413	$82.74	$82.75	$82.70
Purchase #5	$26.69	7.119%	$28.5901	$28.59	$28.60	$28.60
Purchase #6	$57.91	7.404%	$62.1977	$62.20	$62.20	$62.20
Purchase #7	$233.75	13.300%	$264.8388	$264.84	$264.85	$264.80
7 purchase totals =	$795.97		$875.2756	$875.28	$875.30	$875.20